Inverting Device for Liposome Preparation by Centrifugation

ABSTRACT

Methods and devices for producing a population of liposomes are provided. Aspects of the methods include applying a centrifugal force to a suspension of liposomes in a manner sufficient to pass the liposomes through a porous membrane to produce a population of liposomes. Aspects of the invention further include devices, systems and kits useful for performing the methods.

INTRODUCTION

Liposomes are spherical vesicles that have one or multiple lipidbilayers. Liposomes that include a single lipid bilayer may be referredto as unilamellar liposomes, whereas liposomes that include multiplelipid bilayers may be referred to as multilamellar vesicles. Liposomescan be prepared using different methods, which may depend on factors,such as the lipid composition of the lipid bilayer of the liposomes, thetype of medium in which the lipid vesicles are dispersed, the desiredsize of the liposomes, the desired polydispersity of the liposomes, therobustness and batch-to-batch reproducibility of the production method,and other factors, such as the intended use of the resulting liposomes.For example, liposomes may contain a substance, such as a drug, and beused to deliver the substance to a target area in a patient. Thus, themethod used to produce such liposomes may also depend on thephysicochemical characteristics of the substance to be entrapped in theliposomes, the concentration of the entrapped substance, or additionalprocesses involved during application/delivery of the liposomes to thepatient.

After a suspension of liposomes has been produced, such as a suspensionof large, multilamellar vesicles, it may be desirable to produceliposomes having sizes within a certain size range. One common techniquefor sizing liposomes is extrusion, a process by which large,multilamellar vesicles can be disrupted and downsized by extrusionthrough a polycarbonate membrane with defined pore size.

SUMMARY

In this invention we describe an inverting device designed for thepreparation of liposomes by centrifugation. Aspects of this methodinclude applying a centrifugal force to a suspension of liposomes in amanner sufficient to pass the liposomes through a porous membrane toproduce a population of liposomes of a known and restricted size. Inorder to facilitate repeated reciprocal processing the device issymmetrical: two identical collection tubes are connected through porouspolycarbonate membrane holding unit. Aspects of the invention furtherinclude devices, systems and kits useful for performing the methods.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an illustration of an inverting liposome extrusion deviceaccording to embodiments of the present disclosure.

FIG. 2 is an illustration of a system for producing a population ofliposomes according to embodiments of the present disclosure.

DETAILED DESCRIPTION

Methods and devices for producing a population of liposomes areprovided. Aspects of the methods include applying a centrifugal force toa suspension of liposomes in a manner sufficient to pass the liposomesthrough a porous membrane to produce a population of liposomes. Aspectsof the invention further include devices, systems and kits useful forperforming the methods.

Before embodiments of the present disclosure are described in greaterdetail, it is to be understood that these embodiments are not limited tothe particular embodiments described, as such may vary. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting, since the scope of the embodiments of the present disclosurewill be limited only by the appended claims.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range, is encompassed within the embodiments of the presentdisclosure. The upper and lower limits of these smaller ranges mayindependently be included in the smaller ranges and are also encompassedwithin the embodiments of the present disclosure, subject to anyspecifically excluded limit in the stated range. Where the stated rangeincludes one or both of the limits, ranges excluding either or both ofthose included limits are also included in the embodiments of thepresent disclosure.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this disclosure belongs. Although any methods andmaterials similar or equivalent to those described herein can also beused in the practice or testing of the embodiments of the presentdisclosure, representative illustrative methods and materials are nowdescribed.

All publications and patents cited in this specification are hereinincorporated by reference as if each individual publication or patentwere specifically and individually indicated to be incorporated byreference and are incorporated herein by reference to disclose anddescribe the methods and/or materials in connection with which thepublications are cited. The citation of any publication is for itsdisclosure prior to the filing date and should not be construed as anadmission that the embodiments of the present disclosure are notentitled to antedate such publication by virtue of prior invention.Further, the dates of publication provided may be different from theactual publication dates which may need to be independently confirmed.

It is noted that, as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include plural referents unless thecontext clearly dictates otherwise. It is further noted that the claimsmay be drafted to exclude any optional element. As such, this statementis intended to serve as antecedent basis for use of such exclusiveterminology as “solely,” “only” and the like in connection with therecitation of claim elements, or use of a “negative” limitation.

As will be apparent to those of skill in the art upon reading thisdisclosure, each of the individual embodiments described and illustratedherein has discrete components and features which may be readilyseparated from or combined with the features of any of the other severalembodiments without departing from the scope or spirit of theembodiments of the present disclosure. Any recited method can be carriedout in the order of events recited or in any other order which islogically possible.

As summarized above, the present disclosure provides methods forproducing a population of liposomes. In further describing embodimentsof the disclosure, the subject methods are first described in greaterdetail. Next, devices useful for performing the methods are described.In addition, systems, as well as kits that include the subject devices,are also provided.

Methods for Producing Liposomes

Aspects of the present disclosure include methods for producing apopulation of liposomes. In some instances, the population of liposomesproduced by the methods is a population of liposomes of defined size. By“defined size” is meant that, because of the manner in which theliposomes are made, the sizes of the various liposomes in the populationare known, and specifically the range of liposome sizes in thepopulation is known. In some cases, the liposomes have an average sizethat is substantially the same. For example, in the case of sphericalliposomes, a population of liposomes may have an average diameter thatis substantially the same. By “average” is meant the arithmetic mean.Values that are substantially the same include values that vary fromeach other by 50% or less, such as 45% or less, or 40% or less, or 35%or less, or 30% or less, or 25% or less, or 20% or less, or 15% or less,or 10% or less, or 5% or less, or 3% or less, or 1% or less, or 0.5% orless. In some cases, values that are substantially the same includevalues that vary from each other by 10% or less. In some cases, valuesthat are substantially the same include values that vary from each otherby 5% or less. In some cases, values that are substantially the sameinclude values that vary from each other by 3% or less. In some cases,values that are substantially the same include values that vary fromeach other by 1% or less. In some cases, values that are substantiallythe same include values that vary from each other by 0.5% or less. Theaverage size of the liposomes may, in some instances, vary by 50% orless, such as 45% or less, or 40% or less, or 35% or less, or 30% orless, or 25% or less, or 20% or less, or 15% or less, or 10% or less, or5% or less, or 3% or less, or 1% or less, or 0.5% or less. In somecases, the average size of the liposomes varies by 10% or less. In somecases, the average size of the liposomes varies by 5% or less. In somecases, the average size of the liposomes varies by 3% or less. In somecases, the average size of the liposomes varies by 1% or less. In somecases, the average size of the liposomes varies by 0.5% or less.

In certain embodiments, a population of liposomes may be described bythe polydispersity of the liposomes. “Dispersity” or “polydispersity” isa measure of the heterogeneity of sizes of particles in a mixture. Inthe context of liposomes, polydispersity can range from 0 to 1, where apolydispersity of 0 indicates a monodisperse population of liposomes(e.g., liposomes that have the same average size), and where apolydispersity of 1 indicates a heterogeneous mixture of liposomes. Insome cases, the size of liposomes (and thus the polydispersity) can bedetermined by dynamic light scattering (DLS).

In certain embodiments, methods of the present disclosure are sufficientfor producing a population of liposomes from a suspension of liposomes(e.g., an aqueous suspension of liposomes). In some cases, the startingsuspension of liposomes includes a population of liposomes havingheterogeneous sizes. As such, methods of the present disclosure includestarting with a suspension of liposomes (e.g., a population of liposomeshaving heterogeneous sizes) and producing a population of liposomes fromthe starting suspension of liposomes.

In some embodiments, the method includes producing a population ofliposomes from a suspension of heterogeneous liposomes, where theaverage size of the resulting population of liposomes varies by 50% orless, such as 45% or less, or 40% or less, or 35% or less, or 30% orless, or 25% or less, or 20% or less, or 15% or less, or 10% or less, or5% or less, or 3% or less, or 1% or less, or 0.5% or less. In somecases, the method includes producing a population of liposomes from asuspension of heterogeneous liposomes, where the average size of theresulting population of liposomes varies by 10% or less. In some cases,the method includes producing a population of liposomes from asuspension of heterogeneous liposomes, where the average size of theresulting population of liposomes varies by 5% or less. In some cases,the method includes producing a population of liposomes from asuspension of heterogeneous liposomes, where the average size of theresulting population of liposomes varies by 3% or less. In some cases,the method includes producing a population of liposomes from asuspension of heterogeneous liposomes, where the average size of theresulting population of liposomes varies by 1% or less. In some cases,the method includes producing a population of liposomes from asuspension of heterogeneous liposomes, where the average size of theresulting population of liposomes varies by 0.5% or less. In yet otherinstances, the average size of the disparate liposome members of thepopulation may vary by 50% or more, such as 75% or more, including 100%or more. For instance, the average size of the disparate liposomemembers in the starting suspension of liposomes may vary by 50% or more,such as 75% or more, including 100% or more.

In some instances, the starting suspension of liposomes has a higherpolydispersity as compared to the produced population of liposomes.Thus, methods of the present disclosure are useful for producing apopulation of liposomes having a polydispersity less than thepolydispersity of the starting suspension of liposomes.

In some cases, the polydispersity of the produced population ofliposomes is 0.9 or less, such as 0.8 or less, or 0.7 or less, or 0.5 orless, or 0.4 or less, or 0.3 or less, or 0.2 or less, or 0.1 or less, or0.05 or less, or 0.01 or less. For example, the polydispersity of theproduced population of liposomes may be 0.5 or less. In some cases, thepolydispersity of the produced population of liposomes may be 0.4 orless. In some cases, the polydispersity of the produced population ofliposomes may be 0.3 or less. In some cases, the polydispersity of theproduced population of liposomes may be 0.2 or less. In some cases, thepolydispersity of the produced population of liposomes may be 0.1 orless. In some cases, the polydispersity of the produced population ofliposomes may be 0.05 or less. In some cases, the polydispersity of theproduced population of liposomes may be 0.01 or less. In certaininstances, the polydispersity of the produced population of liposomesranges from 0.01 to 0.5, such as 0.01 to 0.4, or 0.01 to 0.3, or 0.01 to0.2, or 0.01 to 0.1. In other embodiments, the polydispersity of theproduced population of liposomes ranges from 0.01 to 0.5, such as 0.05to 0.5, or 0.1 to 0.5, or 0.1 to 0.4, or 0.1 to 0.3. In otherembodiments, the polydispersity of the produced population of liposomesranges from 0.01 to 0.5, such as 0.05 to 0.5, or 0.1 to 0.5, or 0.2 to0.5, or 0.2 to 0.4.

In some cases, the polydispersity of the starting suspension ofliposomes is 0.5 or more, such as 0.6 or more, or 0.7 or more, or 0.8 ormore, or 0.9 or more. In some cases, the polydispersity of the startingsuspension of liposomes is 1. For example, the polydispersity of thestarting suspension of liposomes may range from 0.5 to 1, such as 0.6 to1, or 0.7 to 1, or 0.8 to 1, or 0.9 to 1.

In some instances, the starting suspension of liposomes includesliposomes having sizes larger than the produced population of liposomes.In some instances, the starting suspension of liposomes includesliposomes having an average size (e.g., an average diameter) of 500 nmor more, such as 600 nm or more, or 700 nm or more, or 800 nm or more,or 900 nm or more, or 1000 nm or more, or 1250 nm or more, or 1500 nm ormore, or 1750 nm or more, or 2000 nm or more, or 2250 nm or more, or2500 nm or more, or 2750 nm or more, or 3000 nm or more, where in someinstances the size is 5000 nm or less, such as 4000 nm or less,including 3000 nm or less. For example, the starting suspension ofliposomes may include large multilamellar vesicles (LMVs), e.g.,multilamellar vesicles having an average size of 200 nm or more, such asranging from 200 nm to 3,000 nm. In some instances, the startingsuspension of liposomes may include large unilamellar vesicles (LUVs),e.g., unilamellar vesicles having an average size of 100 nm or more,such as ranging from 100 nm to 1000 nm.

In some cases, embodiments of the methods may include a step ofproducing the starting suspension of liposomes. As described above, thesuspension of liposomes may be heterogeneous with respect to the sizesof the liposomes in the suspension of liposomes. The suspension ofheterogeneous liposomes may be produced using any convenient method forproducing liposomes, such as, but not limited to, a solvent dispersionprocess (e.g., Bangham method, which includes the dissolution of lipidsin an organic solvent and then removal of the organic solvent, such asby evaporation of the organic solvent), a detergent removal process(e.g., where detergent-lipid micelles are formed, followed by removal ofthe detergent to form the liposomes), an injection process (e.g., wherelipids are dissolved in an organic solvent and the resulting lipidsolution is injected into an aqueous media), a microfluidic process(e.g., where a stream of lipids dissolved in an organic solvent ispassed between two aqueous streams in a microfluidic channel), amechanical dispersion process, a sonication process, combinationsthereof, and the like.

Liposomes useful in embodiments of the present disclosure are composedof lipids. In certain embodiments, the lipids are amphiphilic.Amphiphilic lipids may include a hydrophilic group and one or morelipophilic groups covalently bonded to the hydrophilic group. In somecases, the hydrophilic group is a charged group, such as an anionicgroup or a cationic group. In some instances, the hydrophilic group isan uncharged, polar group. In some embodiments, the hydrophilic groupincludes a charged group and a polar group. Examples of hydrophilicgroups include, but are not limited to, phosphate, phosphocholine,phosphoglycerol, phosphoethanolamine, phosphoserine, phosphoinositol,ethylphosphosphorylcholine, polyethyleneglycol, polyglycerol,sphingosine, phosphoshingosine, tri-nitrilotriacetic acid, melamine,glucosamine, trimethylamine, spermine, spermidine, and conjugatedcarboxylates, sulfates, boric acid, sulfonates, sulfates, carbohydrates,amino acids, and the like. In some cases, the hydrophilic group includesphosphocholine.

In certain embodiments, the lipophilic group includes an aliphaticchain, such as a saturated or unsaturated, linear or branched,substituted or unsubstituted aliphatic chain. For example, thelipophilic group may include an aliphatic chain of 2 to 40 carbon atomsin length, and may be saturated or unsaturated, linear or branched,substituted or unsubstituted. For instance, the lipophilic group mayinclude a saturated or unsaturated, linear or branched, substituted orunsubstituted hydrocarbon chain having from 2 to 40 carbon atoms, suchas from 4 to 30 carbon atoms, or from 4 to 25 carbon atoms, or from 6 to24 carbon atoms, or from 10 to 20 carbon atoms. In certain cases, thelipophilic group includes a saturated or unsaturated, linear or branchedhydrocarbon chain having 18 carbon atoms. In certain cases, thelipophilic group includes a saturated or unsaturated, linear or branchedhydrocarbon chain having 16 carbon atoms. In embodiments where the lipidincludes more than one lipophilic group, the lipophilic groups may bethe same, or in other cases may be different. Liposomes may be composedof the same type of lipid or combinations of two or more different typesof lipids.

Embodiments of the liposomes may include liposomes having a detectablelabel. In some cases, the detectable label is stably associated with asupport. By “stably associated” is meant that a moiety is bound to orotherwise associated with another moiety or structure under standardconditions. Bonds may include covalent bonds and non-covalentinteractions, such as, but not limited to, ionic bonds, hydrophobicinteractions, hydrogen bonds, van der Waals forces (e.g., Londondispersion forces), dipole-dipole interactions, and the like. In certainembodiments, the detectable label is covalently bound to the liposome.For instance, as described above, lipids that comprise the liposome mayinclude a hydrophilic group, which, in some cases may include anactivated functional group that provides for a covalent attachment tothe detectable label. Any convenient activated functional group usefulin chemical synthesis may be used to covalently bond the detectablelabel to the hydrophilic group of a lipid, such as, but not limited to,amine, carboxyl, amide, hydroxy, azide, maleimide, bromoacetyl,2-pyridyldithiol, haloalkyl, alkene, or propargyl, or the like.

Liposomes according to embodiments of the present disclosure can includea payload associated with the liposome. As used herein, “payload” refersto a component that is contained within the structure of a liposome,present in a bilayer of lipid particles, or attached to a surface of aliposome (e.g., by a covalent bond or non-covalent interaction). Thus, apayload can include components that are encapsulated by the liposome(e.g., pharmaceutically active agents, nutriceutical agents,cosmeceutical agents, imaging agents, radiopharmaceutical agents,nuclear magnetic resonance contrast agents, and the like). In certainembodiments, the encapsulated payload is in solution, or may be presentas a crystal, as a powder, or a combination thereof. For example, inembodiments where it is desired to provide liposomes with anencapsulated payload (e.g., an encapsulated agent, a therapeutic agent,imaging agent, or the like), such agents may be included in an aqueousphase inside the liposome. Alternatively, in embodiments where the agentis hydrophobic and thus less soluble in water, the hydrophobic agent canbe included within a portion of the lipid bilayer.

Embodiments of the methods may also include preparing a liposomeextrusion device for use in the method of producing a population ofliposomes. Generally, a liposome extrusion device according toembodiments of the present disclosure includes a first liquid container,a second liquid container in fluid communication with the first liquidcontainer, a porous membrane, and a component configured to position themembrane between the first liquid container and the second liquidcontainer. More detailed aspects of the liposome extrusion device aredescribed in the Devices section below. The component configured toposition the membrane between the first liquid container and the secondliquid container may also be referred to herein as a membrane componentor a membrane support. In some instances, the membrane componentsupports the membrane in a position between the first liquid containerand the second liquid container. In some cases, the membrane componentis removable from the first liquid container. In some cases, themembrane component is removable from the second liquid container. Insome cases, the membrane component is removable from both the firstliquid container and the second liquid container. As such, embodimentsof the method may include positioning the membrane component between thefirst liquid container and the second liquid container, and thuspositioning the membrane between the first liquid container and thesecond liquid container. For example, the membrane component may bepositioned on an open end of the first liquid container and/or on anopen end of the second liquid container. Prior to positioning themembrane component on an open end of the first liquid container and/oron an open end of the second liquid container, a suspension of liposomesmay be introduced into the liposome extrusion device from which thepopulation of liposomes is produced.

Embodiments of the method for producing a population of liposomesinclude introducing a suspension of liposomes into the liposomeextrusion device. The suspension of liposomes may be introduced into theliposome extrusion device by introducing the suspension of liposomesinto either the first liquid container or the second liquid container.For example, in some instances, the suspension of liposomes isintroduced into the liposome extrusion device by introducing thesuspension of liposomes into the first liquid container. In otherinstances, the suspension of liposomes is introduced into the liposomeextrusion device by introducing the suspension of liposomes into thesecond liquid container.

In certain embodiments, the method also includes positioning themembrane between the first liquid container and the second liquidcontainer. For instance, since the membrane is supported and containedwithin the membrane component as described above, the method may includepositioning the membrane component between the first liquid containerand the second liquid container, which in turn results in positioningthe membrane itself between the first liquid container and the secondliquid container. In some cases, positioning the membrane includesconnecting the membrane component to the first liquid container and/orthe second liquid container. For example, the membrane component may beconnected to the liquid container containing the suspension ofliposomes. In some instances, positioning the membrane includesconnecting the membrane component to the first liquid container (e.g.,where the first liquid container contains the suspension of liposomes).In some instances, positioning the membrane includes connecting themembrane component to the second liquid container (e.g., where thesecond liquid container contains the suspension of liposomes). Forexample, the membrane component may be connected to an open end of thefirst liquid container and/or the second liquid container. In somecases, the membrane component is connected to an open end of the liquidcontainer containing the suspension of liposomes. For instance, themembrane component may be connected to an open end of the first liquidcontainer. In some instances, the membrane component may be connected toan open end of the second liquid container. Positioning the membrane mayfurther include connecting the other liquid container to the membranecomponent. For example, positioning the membrane may include connectingthe liquid container that is not already connected to the membranecomponent. The other liquid container may be empty, or in other casesmay contain a suspension of liposomes. The membrane component may beconnected to an open end of the other liquid container. In someinstances, the other liquid container is connected to an end of themembrane component opposing the end where the first liquid container isconnected. As such, an assembled liposome extrusion device includes afirst liquid container connected to one end of the membrane componentand a second liquid container connected to a second opposing end of themembrane component. Either one, or both, the first liquid container orthe second liquid container may contain the suspension of liposomes.

In certain embodiments, the first liquid container is in fluidcommunication with the second liquid container. In some cases, the firstliquid container is in fluid communication with the membrane componentand the second liquid container. In some cases, the second liquidcontainer is in fluid communication with the membrane component and thefirst liquid container. In some cases, the first liquid container, themembrane component, and the second liquid container are in fluidcommunication with each other. By fluid communication is meant that afluid (e.g., a gas or a liquid, including a suspension of liposomes) isable to flow from one area to another area. For example, in a liposomeextrusion device disclosed herein, a fluid may flow from the firstliquid container to the second liquid container. Since the membrane ispositioned between the first liquid container and the second liquidcontainer, fluid communication between the first liquid container andthe second liquid container allows the fluid (e.g., suspension ofliposomes) to flow through the membrane as the fluid flows from thefirst liquid container to the second liquid container or from the secondliquid container to the first liquid container.

In certain embodiments, the suspension of liposomes may be introducedinto the liposome extrusion device such that the suspension of liposomesis positioned on one side of the membrane. For example, the suspensionof liposomes may be contained in the first liquid container, which ispositioned on one side of the membrane. During production of thepopulation of liposomes, the suspension of liposomes may traverse fromone side of the membrane, through the porous membrane, and to the otherside of the membrane. For instance, the suspension of liposomes may becontained initially in the first liquid container on a first side of themembrane and then, during production of the population of liposomes, maytraverse the porous membrane to be contained in the second liquidcontainer on the other side of the membrane. In some cases, thesuspension of liposomes may be contained initially in the second liquidcontainer on a second side of the membrane and then, during productionof the population of liposomes, may traverse the porous membrane to becontained in the first liquid container on the first side of themembrane. In other cases, the suspension of liposomes may be containedinitially in both the first liquid container and the second liquidcontainer and then, during production of the population of liposomes,may traverse the porous membrane from either the first liquid containerto the second liquid container, or vice versa.

In certain aspects, the suspension of liposomes is introduced into theliposome extrusion device using any convenient liquid handlingtechnique. For example, a volume of the suspension of liposomes may beadded to the liposome extrusion device using any convenient liquidhandling apparatus, such as, but not limited to, a syringe, a needle, apipette, an aspirator, among other liquid handling devices.

Methods of the present disclosure are useful for producing a populationof liposomes as described above, e.g., a population of liposomes ofdefined size. In some embodiments, the population of liposomes has anaverage size less than the average size of the starting suspension ofliposomes. In some cases, the produced population of liposomes has anaverage size (e.g., an average diameter) of 1000 nm or less, such as 900nm or less, or 800 nm or less, or 700 nm or less, or 600 nm or less, or500 nm or less, or 400 nm or less, or 300 nm or less, or 250 nm or less,or 200 nm or less, or 150 nm or less, or 100 nm or less, or 75 nm orless, or 50 nm or less, or 25 nm or less, or 20 nm or less, or 15 nm orless, or 10 nm or less, or 5 nm or less, or 1 nm or less, where in someinstances the size average size is 1 nm or more, such as 5 nm or more.In certain instances, the produced population of liposomes has anaverage size of 1000 nm or less. In certain instances, the producedpopulation of liposomes has an average size of 800 nm or less. Incertain instances, the produced population of liposomes has an averagesize of 500 nm or less. In certain instances, the produced population ofliposomes has an average size of 400 nm or less. In certain instances,the produced population of liposomes has an average size of 300 nm orless. In certain instances, the produced population of liposomes has anaverage size of 250 nm or less. In certain instances, the producedpopulation of liposomes has an average size of 200 nm or less. Incertain instances, the produced population of liposomes has an averagesize of 100 nm or less. In certain instances, the produced population ofliposomes has an average size of 50 nm or less. For example, theproduced population of liposomes may include small unilamellar vesicles(SUVs), e.g., unilamellar vesicles having an average size of 100 nm orless, such as ranging from 10 nm to 100 nm.

In order to produce the population of liposomes, methods of the presentdisclosure involve the use of a liposome extrusion device as describedherein. As described above, in certain embodiments, the membrane of theliposome extrusion device is a porous membrane and the method includespassing the suspension of liposomes (e.g., a heterogeneous population ofliposomes) through the porous membrane to produce a population ofliposomes (e.g., a population of liposomes having a defined size). Incertain embodiments, passing the suspension of liposomes through themembrane includes applying a force on the suspension of liposomes suchthat the liposomes traverse from one side of the membrane to the otherside of the membrane. As the liposomes traverse the membrane, theliposomes pass through the pores in the porous membrane to produce thepopulation of liposomes. The embodiments of the method include extrudinga population of liposomes from the porous membrane. In certaininstances, the starting suspension of liposomes has an average size thatis larger than the pores of the membrane. In some instances, passinglarger-sized liposomes through smaller-sized pores in the membraneresizes the liposomes to an average size approximately the same as thesize of the pores of the membrane. Thus, in certain cases, passing theliposomes through the membrane produces a population of liposomes (e.g.,a population of liposomes having a defined size).

In some instances, applying a force on the suspension of liposomesincludes applying a centrifugal force to the suspension of liposomes ina manner sufficient to pass the liposomes through the membrane toproduce a population of liposomes. For example, the method may includethe use of a centrifuge, where the liposome extrusion device containingthe suspension of liposomes is placed in the centrifuge and thecentrifuge is operated in a manner sufficient to apply a centrifugalforce on the suspension of liposomes. The centrifugal force may beapplied to the suspension of liposomes such that the liposomes areforced through the pores of the membrane as described above, thusextruding a population of liposomes from the membrane. As such, in somecases, the method includes spinning the suspension of liposomes in acentrifuge. The suspension of liposomes may be contained in a liposomeextrusion device containing the membrane, and thus the method mayinclude spinning the liposome extrusion device containing the suspensionof liposomes in a centrifuge such that the liposomes are forced throughthe pores of the membrane as described above.

In certain embodiments, applying the centrifugal force results inpositioning the population of liposomes in one of the liquid containers.For example, as described above, applying the centrifugal force resultsin the suspension of liposomes traversing from one liquid container intothe other liquid container, and thus applying the centrifugal forcepositions the suspension of liposomes in the liquid container opposingthe liquid container the suspension of liposomes was initially containedin. As such, applying the centrifugal force may include positioning theliposome extrusion device in a centrifuge such that a liquid containercontaining the suspension of liposomes is positioned proximal (e.g.,closer) to the axis of rotation of the centrifuge and an opposing liquidcontainer is positioned distal (e.g., further away) from the axis ofrotation. When the centrifugal force is applied (e.g., by spinning theliposome extrusion device in the centrifuge) the centrifugal force isapplied to the suspension of liposomes to force the suspension ofliposomes from the proximal liquid container into the distal liquidcontainer, thus traversing the membrane between the liquid containers.

Some embodiments of the subject methods include applying the centrifugalforce to the suspension of liposomes a single time in a mannersufficient to pass the liposomes through the membrane to produce apopulation of liposomes. In certain embodiments, the method forproducing a population of liposomes includes repeating the applicationof the centrifugal force one or more times. As such, certain embodimentsof the method include methods where applying the centrifugal force isrepeated one or more times to produce the population of liposomes. Forexample, applying the centrifugal force may be repeated 1 or more times,such as 2 or more times, or 3 or more times, or 4 or more times, or 5 ormore times, or 6 or more times, or 7 or more times, or 8 or more times,or 9 or more times, or 10 or more times, including 15 or more times, or20 or more times, or 25 or more times. As such, certain embodiments ofthe method include passing the suspension of liposomes through theporous membrane one or more times to produce a population of liposomes.For instance, certain embodiments of the method include passing thesuspension of liposomes through the porous membrane 1 or more times,such as 2 or more times, or 3 or more times, or 4 or more times, or 5 ormore times, or 6 or more times, or 7 or more times, or 8 or more times,or 9 or more times, or 10 or more times, including 15 or more times, or20 or more times, or 25 or more times to produce a population ofliposomes (e.g., a population of liposomes having a defined size).

As described above, when applying the centrifugal force, the liposomeextrusion device is positioned in the centrifuge such that the liquidcontainer containing the suspension of liposomes is positioned proximal(e.g., closer) to the axis of rotation of the centrifuge and theopposing liquid container is positioned distal (e.g., further away) fromthe axis of rotation. Thus, in embodiments where applying thecentrifugal force is repeated one or more times, the method may includeinverting the liposome extrusion device after applying the centrifugalforce, such that the liposome extrusion device is inverted beforeapplying the next centrifugal force. In some cases, the method includesinverting the liposome extrusion device between each repetition ofapplying the centrifugal force. In certain instances, inverting theliposome extrusion device includes inverting the position of theliposome extrusion device in the centrifuge. In certain instances,inverting the liposome extrusion device includes inverting theorientation of the liposome extrusion device in the centrifuge. Forexample, inverting the position of the liposome extrusion device in thecentrifuge may include removing the liposome extrusion device from thecentrifuge and inserting the liposome extrusion device back into thecentrifuge in an orientation opposite from the orientation of theliposome extrusion device before the liposome extrusion device wasremoved from the centrifuge. For instance, the liposome extrusion devicemay initially contain the suspension of liposomes in the first liquidcontainer and be positioned in the centrifuge with the first liquidcontainer proximal (e.g., closer) to the axis of rotation of thecentrifuge and the opposing second liquid container positioned distal(e.g., further away) from the axis of rotation of the centrifuge. Uponapplication of the centrifugal force, as described above, the suspensionof liposomes traverses from the first liquid container to the secondliquid container such that the suspension of liposomes is extruded fromthe first liquid container into the second liquid container through themembrane. As such, the suspension of liposomes will be contained in thesecond liquid container. The liposome extrusion device may then beinverted, for example by removing the liposome extrusion device from thecentrifuge and reinserting the liposome extrusion device into thecentrifuge in an opposite orientation, such that the second liquidcontainer (e.g., the liquid container now containing the suspension ofliposomes) is positioned in the centrifuge proximal (e.g., closer) tothe axis of rotation of the centrifuge and the opposing first liquidcontainer is positioned distal (e.g., further away) from the axis ofrotation of the centrifuge. Application of the centrifugal force wouldthen cause the suspension of liposomes to be extruded from the secondliquid container into the first liquid container through the membrane,such that the suspension of liposomes is contained in the first liquidcontainer. Repeated alternations of applying the centrifugal force andinverting the liposome extrusion device in the centrifuge can beperformed to produce a desired population of liposomes (e.g., apopulation of liposomes having a defined size).

In certain embodiments, applying a centrifugal force to the suspensionof liposomes includes applying a centrifugal force sufficient to causethe liposomes to pass through the pores of the membrane. In some cases,the applied centrifugal force is greater than standard gravity, such asfor example 2 g or more, or 5 g or more, or 10 g or more, or 25 g ormore, or 50 g or more, or 100 g or more, or 250 g or more, or 500 g ormore, or 750 g or more, or 1000 g or more, or 1500 g or more, or 2000 gor more, or 2500 g or more, or 3000 g or more, or 3500 g or more, or4000 g or more, or 4500 g or more, or 5000 g or more, or 5500 g or more,or 6000 g or more, or 6500 g or more, or 7000 g or more, or 7500 g ormore, or 8000 g or more, or 8500 g or more, or 9000 g or more, or 9500 gor more, or 10,000 g or more.

As described above, in some cases, applying a centrifugal force includesspinning the liposome extrusion device containing the suspension ofliposomes in a centrifuge, and thus in these embodiments, applying asufficient centrifugal force may include spinning at 10 rpm or more,such as 50 rpm or more, or 100 rpm or more, or 250 rpm or more, or 500rpm or more, or 750 rpm or more, or 1000 rpm or more, or 1500 rpm ormore, or 2000 rpm or more, or 2500 rpm or more, or 3000 rpm or more, or3500 rpm or more, or 4000 rpm or more, or 4500 rpm or more, or 5000 rpmor more, or 5500 rpm or more, or 6000 rpm or more, or 6500 rpm or more,or 7000 rpm or more, or 7500 rpm or more, or 8000 rpm or more, or 8500rpm or more, or 9000 rpm or more, or 9500 rpm or more, or 10,000 rpm ormore.

In some instances, the centrifugal force is applied for a certain amountof time. The amount of time the centrifugal force is applied may be atime equal to or greater than the time needed for the suspension ofliposomes to pass through the pores of the membrane at the appliedcentrifugal force. For example, the method may include applying acentrifugal force for a time such as 1 min or more, or 2 min or more, or3 min or more, or 4 min or more, or 5 min or more, or 6 min or more, or7 min or more, or 8 min or more, or 10 min or more. In some cases, themethod may include applying a centrifugal force for a time such as 10min or less, or 9 min or less, or 8 min or less, or 7 min or less, or 6min or less, or 5 min or less, or 4 min or less, or 3 min or less, or 2min or less, or 1 min or less.

In certain embodiments, because a centrifugal force is applied to causethe liposomes to traverse the porous membrane, the methods of thepresent disclosure may be performed at atmospheric pressure. In somecases, the subject method includes applying the centrifugal force atatmospheric pressure. For example, methods of the present disclosure maynot require a pressure greater than atmospheric pressure to be appliedto the suspension of liposomes. In some cases, using methods of thepresent disclosure, a population of liposomes is produced at standardatmospheric pressure. Thus, certain embodiments of the subject methodsdo not include applying a pressure on the suspension of liposomes, e.g.,either manually or by increasing the pressure of a gas or liquidcontacting the suspension of liposomes.

In certain embodiments, the method includes sealing the liposomeextrusion device prior to applying the centrifugal force. Sealing theliposome extrusion device may facilitate retention of the suspension ofliposomes inside the liposome extrusion device while the centrifugalforce is being applied. For example, as described above, the method mayinclude connecting the membrane component to the first liquid containerand the second liquid container. In some cases, connecting the membranecomponent to the first liquid container may facilitate the production ofa seal, such as a substantially liquid-tight and/or substantiallygas-tight seal, between the first liquid container and the membranecomponent. In some cases, connecting the membrane component to thesecond liquid container may facilitate the production of a seal, such asa substantially liquid-tight and/or substantially gas-tight seal,between the second liquid container and the membrane component. As such,the liposome extrusion device, and each component thereof (e.g., firstliquid container, second liquid container and membrane component), maybe substantially liquid-tight and/or substantially gas-tight. By“liquid-tight” is meant that a liquid contained inside the liposomeextrusion device does not substantially leak out of the liposomeextrusion device and that a liquid outside the liposome extrusion devicedoes not substantially enter into the liposome extrusion device. By“gas-tight” is meant that a gas contained inside the liposome extrusiondevice does not substantially leak out of the liposome extrusion deviceand that a gas outside the liposome extrusion device does notsubstantially enter into the liposome extrusion device. Thus, in certainembodiments, the liposome extrusion device is a sealed liposomeextrusion device, such as a liquid-tight and/or gas-tight liposomeextrusion device. As such, an interior of the liposome extrusion devicemay be sealed from the surrounding atmosphere. For example, the interiorof the first liquid container, the interior of the second liquidcontainer and the interior of the membrane component may be sealed fromthe surrounding atmosphere. In some instances, the method may includeunsealing the liposome extrusion device prior to introducing a volume ofthe suspension of liposomes into the liposome extrusion device.Unsealing the liposome extrusion device may expose the contents of theliposome extrusion device to the surrounding environment and allowaccess to the interior volume of the liposome extrusion device. Thus, auser that has access to the interior volume of the liposome extrusiondevice may introduce the volume of the suspension of liposomes into theliposome extrusion device for producing the population of liposomes asdescribed above. In some cases, unsealing the liposome extrusion deviceincludes disconnecting the first liquid container from the membranecomponent to expose the interior of the first liquid container. In somecases, unsealing the liposome extrusion device includes disconnectingthe second liquid container from the membrane component to expose theinterior of the second liquid container.

In certain embodiments, the method also includes mixing the contents ofthe liposome extrusion device after introducing the suspension ofliposomes into the liposome extrusion device. The mixing may beperformed using any convenient protocol. For example, the mixing may beperformed using an agitator. The agitator may be any convenient agitatorsufficient for mixing a liquid inside a liquid container, including, butnot limited to, vortexers, sonicators, shakers (e.g., manual,mechanical, or electrically powered shakers), rockers, oscillatingplates, magnetic stirrers, static mixers, rotators, blenders, mixers,tumblers, orbital shakers, among other agitating protocols. In somecases, the method also includes assaying the produced population ofliposomes. Assaying the population of liposomes may be performed usingany suitable assay apparatus. For example, the assay may be an assay fordetermining the average size of the population of liposomes, thepolydispersity of the population of liposomes, or a combination thereof.In some cases, the assay may be performed by dynamic light scattering(DLS). In some cases, the assay apparatus may be a flow cytometer. Inthese embodiments, the assaying includes flow cytometrically analyzingthe population of liposomes. In certain embodiments, the liposomesinclude a fluorescent label, and thus certain embodiments of theassaying include contacting the population of liposomes withelectromagnetic radiation (e.g., light), such as electromagneticradiation having a wavelength that corresponds to an excitation maximaof the fluorescent label of the liposomes. The assaying may furtherinclude detecting emitted light from the excited fluorescent label. Forinstance, the method may include detecting emitted light from theexcited fluorescent label at one or more wavelengths that correspond tothe emission maxima of the fluorescent label. In certain embodiments,the population of liposomes may be used in methods for calibrating aflow cytometer, e.g., the population of liposomes may be used as acalibration standard for a flow cytometer.

In certain embodiments, the fluorescent label includes one or moredetectable moieties or markers that are detectible based on, forexample, fluorescence emission maxima, fluorescence polarization,fluorescence lifetime, light scatter, mass, molecular mass, orcombinations thereof. In certain embodiments, the fluorescent labelincludes a fluorophore (i.e., a fluorescent label, fluorescent dye,etc.). Fluorophores of interest may include but are not limited to dyessuitable for use in analytical applications (e.g., flow cytometry,imaging, etc.). A large number of dyes (e.g., non-polymeric dyes) arecommercially available from a variety of sources, such as, for example,Molecular Probes (Eugene, Oreg.) and Exciton (Dayton, Ohio). Forexample, the fluorophore of the dye may be4-acetamido-4′-isothiocyanatostilbene-2,2′disulfonic acid; acridine andderivatives such as acridine, acridine orange, acrindine yellow,acridine red, and acridine isothiocyanate;5-(2′-aminoethyl)aminonaphthalene-1-sulfonic acid (EDANS);4-amino-N-[3-vinylsulfonyl)phenyl]naphthalimide-3,5 disulfonate (LuciferYellow VS); N-(4-anilino-1-naphthyl)maleimide; anthranilamide; BrilliantYellow; coumarin and derivatives such as coumarin,7-amino-4-methylcoumarin (AMC, Coumarin 120),7-amino-4-trifluoromethylcouluarin (Coumaran 151); cyanine andderivatives such as cyanosine, Cy3, Cy3.5, Cy5, Cy5.5, and Cy7;4′,6-diaminidino-2-phenylindole (DAPI); 5′,5″-dibromopyrogallol-sulfonephthalein (Bromopyrogallol Red);7-diethylamino-3-(4′-isothiocyanatophenyl)-4-methylcoumarin;diethylaminocoumarin; diethylenetriamine pentaacetate;4,4′-diisothiocyanatodihydro-stilbene-2,2′-disulfonic acid;4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid;5-[dimethylamino]naphthalene-1-sulfonyl chloride (DNS, dansyl chloride);4-(4′-dimethylaminophenylazo)benzoic acid (DABCYL);4-dimethylaminophenylazophenyl-4′-isothiocyanate (DABITC); eosin andderivatives such as eosin and eosin isothiocyanate; erythrosin andderivatives such as erythrosin B and erythrosin isothiocyanate;ethidium; fluorescein and derivatives such as 5-carboxyfluorescein(FAM), 5-(4,6-dichlorotriazin-2-yl)aminofluorescein (DTAF),2′7′-dimethoxy-4′5′-dichloro-6-carboxyfluorescein (JOE), fluoresceinisothiocyanate (FITC), fluorescein chlorotriazinyl, naphthofluorescein,and QFITC (XRITC); fluorescamine; IR144; IR1446; Green FluorescentProtein (GFP); Reef Coral Fluorescent Protein (RCFP); Lissamine™;Lissamine rhodamine, Lucifer yellow; Malachite Green isothiocyanate;4-methylumbelliferone; ortho cresolphthalein; nitrotyrosine;pararosaniline; Nile Red; Oregon Green; Phenol Red; B-phycoerythrin(PE); o-phthaldialdehyde; pyrene and derivatives such as pyrene, pyrenebutyrate and succinimidyl 1-pyrene butyrate; Reactive Red 4 (Cibacron™Brilliant Red 3B-A); rhodamine and derivatives such as6-carboxy-X-rhodamine (ROX), 6-carboxyrhodamine (R6G),4,7-dichlororhodamine lissamine, rhodamine B sulfonyl chloride,rhodamine (Rhod), rhodamine B, rhodamine 123, rhodamine Xisothiocyanate, sulforhodamine B, sulforhodamine 101, sulfonyl chloridederivative of sulforhodamine 101 (Texas Red),N,N,N′,N′-tetramethyl-6-carboxyrhodamine (TAMRA), tetramethyl rhodamine,and tetramethyl rhodamine isothiocyanate (TRITC); riboflavin; rosolicacid and terbium chelate derivatives; xanthene; carotenoid-proteincomplexes, such as peridinin-chlorophyll proteins (PerCP);allophycocyanin (APC); or combinations thereof.

Suitable flow cytometry systems and methods for analyzing samples thatmay be employed in methods of the invention include, but are not limitedto those described in Ormerod (ed.), Flow Cytometry: A PracticalApproach, Oxford Univ. Press (1997); Jaroszeski et al. (eds.), FlowCytometry Protocols, Methods in Molecular Biology No. 91, Humana Press(1997); Practical Flow Cytometry, 3rd ed., Wiley-Liss (1995); Virgo, etal. (2012) Ann Clin Biochem. January; 49(pt 1):17-28; Linden, et. al.,Semin Throm Hemost. 2004 October; 30(5):502-11; Alison, et al. J Pathol,2010 December; 222(4):335-344; and Herbig, et al. (2007) Crit Rev TherDrug Carrier Syst. 24(3):203-255; the disclosures of which areincorporated herein by reference. In certain instances, flow cytometrysystems of interest include BD Biosciences FACSCanto™ and FACSCanto II™flow cytometers, BD Biosciences FACSVantage^(m), BD BiosciencesFACSort™, BD Biosciences FACSCount™, BD Biosciences FACScan™, and BDBiosciences FACSCalibur™ systems, BD Biosciences Influx™ cell sorter, BDBiosciences Accuri™ C6 flow cytometer; BD Biosciences LSRFortessa™ flowcytometer, BD Biosciences LSRFortessa™ X-20 flow cytometer, BDBiosciences FACSVerse™ flow cytometer, BD Biosciences FACSAria™ III andBD FACSAria™ Fusion flow cytometers, BD Biosciences FACSJazz™ flowcytometer, or the like. In certain embodiments, the subject systems areflow cytometric systems, such those described in U.S. Pat. Nos.3,960,449; 4,347,935; 4,667,830; 5,245,318; 5,464,581; 5,483,469;5,602,039; 5,643,796; 5,700,692; 6,372,506 and 6,809,804, thedisclosures of which are herein incorporated by reference in theirentirety.

Other methods of analysis may also be used, such as, but not limited to,liquid chromatography-mass spectrometry or gas chromatography-massspectrometry systems. For example, assaying may include the use of ananalytical separation device such as a liquid chromatograph (LC),including a high performance liquid chromatograph (HPLC), a micro- ornano-liquid chromatograph or an ultra-high pressure liquid chromatograph(UHPLC) device, a capillary electrophoresis (CE), or a capillaryelectrophoresis chromatograph (CEC) apparatus. Mass spectrometer (MS)systems may also be used to assay the dye compositions. Examples of massspectrometers may include, but are not limited, to electrosprayionization (ESI), atmospheric pressure chemical ionization (APCI),electron impact (EI), atmospheric pressure photoionization (APPI),matrix-assisted laser desorption ionization (MALDI) or inductivelycoupled plasma (ICP) ionization, for example, or any combinationthereof. Likewise, any of a variety of different mass analyzers may beemployed, including time of flight (TOF), Fourier transform ioncyclotron resonance (FTICR), ion trap, quadrupole or double focusingmagnetic electric sector mass analyzers, or any hybrid thereof.

In certain embodiments, the method also includes storing the liposomesfor a period of time. The liposomes may be stored for a period of timebefore and/or after producing the population of liposomes. In someinstances, the liposomes are stored for a period of time such as 1 houror more, or 4 hours or more, or 6 hours or more, or 12 hours or more, or18 hours or more, or 24 hours or more, or 48 hours or more, or 72 hoursor more, or 4 days or more, or 5 days or more, or 6 days or more, or 1week or more.

Embodiments of the method may further include shipping the liposomes toa remote location. A “remote location,” is a location other than thelocation at which the liposomes are produced. For example, a remotelocation could be another location (e.g., office, lab, etc.) in the samecity, another location in a different city, another location in adifferent state, another location in a different country, etc. As such,when one item is indicated as being “remote” from another, what is meantis that the two items can be in the same room but separated, or at leastin different rooms or different buildings, and can be at least one mile,ten miles, or one hundred miles or more apart.

Liposome Extrusion Devices

Aspects of the present disclosure include liposome extrusion devices. Aliposome extrusion device of the present disclosure is useful for theproduction of a population of liposomes. Liposome extrusion devicesaccording to certain embodiments of the present disclosure include aporous membrane and a component configured to position the membranebetween a first liquid container and a second liquid container. In someinstances, when the component is attached to the first liquid containerand the second liquid container, an interior of the liposome extrusiondevice is sealed from the surrounding atmosphere. For example, aninterior of the first liquid container, an interior of the second liquidcontainer and an interior of the component may be sealed from thesurrounding atmosphere. Further aspects of each of the elements of theliposome extrusion device are described in more detail below.

As indicated above, the liposome extrusion device includes a porousmembrane. A porous membrane is a membrane that includes a plurality ofpores in the membrane. The pores may be pores that have defined poresizes. The size of a pore may be measured as a dimension of the openingof the pore, such as the largest dimension of the opening of the pore.For example, in some cases, the pore is an opening in the membranehaving a substantially circular cross section. Thus, in these cases, thepore size can be measured as the diameter of the pore. For instance, thepores in the membrane may have a pore size (e.g., an average pore size)of 1000 nm or less, such as 900 nm or less, or 800 nm or less, or 700 nmor less, or 600 nm or less, or 500 nm or less, or 400 nm or less, or 300nm or less, or 250 nm or less, or 200 nm or less, or 150 nm or less, or100 nm or less, or 75 nm or less, or 50 nm or less, or 25 nm or less, or20 nm or less, or 15 nm or less, or 10 nm or less, or 5 nm or less, or 1nm or less. In certain instances, the membrane pores have an averagepore size of 1000 nm or less. In certain instances, the membrane poreshave an average pore size of 900 nm or less. In certain instances, themembrane pores have an average pore size of 800 nm or less. In certaininstances, the membrane pores have an average pore size of 700 nm orless. In certain instances, the membrane pores have an average pore sizeof 600 nm or less. In certain instances, the membrane pores have anaverage pore size of 500 nm or less. In certain instances, the membranepores have an average pore size of 400 nm or less. In certain instances,the membrane pores have an average pore size of 300 nm or less. Incertain instances, the membrane pores have an average pore size of 250nm or less. In certain instances, the membrane pores have an averagepore size of 200 nm or less. In certain instances, the membrane poreshave an average pore size of 150 nm or less. In certain instances, themembrane pores have an average pore size of 100 nm or less. In certaininstances, the membrane pores have an average pore size of 75 nm orless. In certain instances, the membrane pores have an average pore sizeof 50 nm or less. In certain instances, the membrane pores have anaverage pore size of 25 nm or less. In certain instances, the membranepores have an average pore size of 20 nm or less. In certain instances,the membrane pores have an average pore size of 15 nm or less. Incertain instances, the membrane pores have an average pore size of 10 nmor less. In certain instances, the membrane pores have an average poresize of 5 nm or less. In certain instances, the membrane pores have anaverage pore size of 1 nm or less. In some embodiments, the pores in themembrane are substantially the same size. Stated another way, the poresin the membrane may be uniform in size. A porous membrane that includesuniformly sized pores may facilitate the production of a population ofliposomes having a defined size.

In certain embodiments, the membrane pores pass through the membrane ina non-tortuous path. For example, the porous membrane may include poreshaving a longitudinal axis substantially perpendicular to a surface ofthe membrane. In some cases, the porous membrane may include poreshaving a longitudinal axis at an angle of less than 90° relative to asurface of the membrane. In certain instances, the porous membrane doesnot include a web-like or matrix construction where a network of poresare interconnected, thus forming a tortuous path through the membrane.Stated another way, the porous membrane may include distinct pores thatpass through the membrane without intersecting other pores in themembrane.

In certain embodiments, the porous membrane is composed of one or morelayers of a membrane material. For example, the membrane may be composedof a single layer of a membrane material. In other embodiments, themembrane is composed of two or more layers of a membrane material. Forinstance, the membrane may include 2 layers of a membrane material, suchas 3 or more layers, or 4 or more layers, or 5 or more layers, or 6 ormore layers, or 7 or more layers, or 8 or more layers, or 9 or morelayers, or 10 or more layers of a membrane material. In some cases, themembrane includes 2 layers of a membrane material. In some cases, themembrane includes 3 layers of a membrane material. In embodiments thatinclude two or more layers of a membrane material, the membrane materialof each layer may be the same, or may be different. In certainembodiments, the pore size of each of the two or more layers of themembrane material is the same. In other embodiments, the pore size of atleast two of the two or more layers of the membrane material aredifferent.

The membrane may be composed of any suitable membrane material. In somecases, the membrane material is compatible with the liquid and/orliposomes in contact with the membrane. For example, the membranematerial can be a liquid-compatible membrane material, such as ahydrophilic membrane material. In some cases, the liposomes may be in anaqueous liquid, and in these cases, the membrane material may becompatible with aqueous media. By “compatible” is meant that themembrane material is substantially inert (e.g., does not significantlyreact with or degrade) in the presence of the liquid and/or liposomes orother ingredients in contact with the membrane. Examples of suitablemembrane materials include polymeric materials, for example, polymers,such as, but not limited to, polycarbonate, polyester, nylon, cellulose,cellulose acetate, polyethylene terephthalate, and the like. In someinstances, the membrane material is polycarbonate. In some instances,the membrane material is polyester.

Embodiments if the subject liposome extrusion devices also include acomponent configured to position the membrane between a first liquidcontainer and a second liquid container. The component configured toposition the membrane between the first liquid container and the secondliquid container may also be referred to as a membrane component or amembrane support herein. In some instances, the membrane componentsupports the membrane in a position between a first liquid container anda second liquid container. The membrane may be substantially planar,e.g., where the suspension of liposomes traverses the membrane in adirection orthogonal to the planar surface of the membrane. In somecases, the component positions the membrane between the first liquidcontainer and the second liquid container such that the plane of themembrane is transverse to a longitudinal axis of the component. Forinstance, the longitudinal axis of the component may be perpendicular tothe plane of the membrane. In some instances, the longitudinal axis ofthe component is aligned with the longitudinal axis of the first liquidcontainer and the longitudinal axis of the second liquid container. Assuch, the component may be configured to position the membrane betweenthe first liquid container and the second liquid container such that theplane of the membrane is transverse to a longitudinal axis of the firstliquid container and transverse to a longitudinal axis of the secondliquid container.

In certain embodiments, the component is configured such that themembrane is positioned between a first end of the component and a secondend of the component. The first end of the component may be an open end,for example that connects to an open end of the first liquid container.The second end of the component may be an open end, for example thatconnects to an open end of the second liquid container.

In some cases, the component may be a single unit. In these embodiments,the membrane may be supported and positioned within the single unit ofthe component. In other embodiments, the component may include two ormore subcomponents, such as a first subcomponent and a secondsubcomponent. The first subcomponent and the second subcomponent may beremovably attached to each other, such that the first subcomponent isremovably attached to the second subcomponent, and the secondsubcomponent is removably attached to the first subcomponent. In someinstances, the membrane is positioned at an interface between the firstsubcomponent and the second subcomponent. The interface between thefirst subcomponent and the second subcomponent may include a surfacehaving one or more holes allowing fluid communication from the firstfluid container through the component to the second fluid container. Insome cases, the interface includes a first surface as part of the firstsubcomponent and a second surface as part of the second subcomponent,with the membrane positioned between the first surface and the secondsurface. Removable attachment of the first subcomponent and the secondsubcomponent facilities access to the membrane, such as for exampleallowing the membrane to be replaced with another membrane. In somecases, the component includes an intra-component connector that connectsthe first subcomponent to the second subcomponent. The intra-componentconnector can be any suitable connector, such as, but not limited toscrew threads, clips, snaps, pressure fittings, and the like. Forinstance, in some cases, the first subcomponent includes anintra-component connector, such as screw threads, on the end of thefirst subcomponent that attaches to the second subcomponent, and thesecond subcomponent includes an intra-component connector, such ascorresponding screw threads, on the end of the second subcomponent thatattaches to the first subcomponent.

In certain embodiments, the membrane component may include a first endand a second end opposing the first end. In some embodiments, the firstend includes a first opening. In some instances, the first opening inthe membrane component exposes a first surface of the membrane. In someembodiments, the second end of the membrane component includes a secondopening. In some instances, the second opening in the membrane componentexposes a second (opposing) surface of the membrane. The membranecomponent may further include one or more side walls, which form thesides of the membrane component between the opening at the first end ofthe membrane component and the opening at the opposing second end of themembrane component. In some instances, there are substantially no gapsbetween the membrane and the side wall(s) of the membrane component,such that the membrane forms a liquid-tight seal against the sidewall(s) of the membrane component. As such, liquid and/or liposomestraversing the membrane may only pass through the pores in the membrane.In certain embodiments, the membrane component is in the shape of acylinder, where the cylinder has a first opening at a first end and asecond opening at a second opposing end of the cylinder. In some cases,the membrane component has a circular cross section. As such, themembrane may also have a circular shape.

As described above, the component may be connected to the first liquidcontainer and the second liquid container. As such, in certainembodiments, the component includes a first connector for connecting thecomponent to the first liquid container, and a second connector forconnecting the component to the second liquid container. The firstconnector and the second connector may be positioned on opposing ends ofthe component. The first and second connectors can be any suitableconnectors, such as, but not limited to screw threads, clips, snaps,pressure fittings, and the like. For instance, in some cases, thecomponent includes a first connector, such as screw threads, on the endof the component that attaches to the first liquid container, and thefirst liquid container includes a corresponding connector, such ascorresponding screw threads, on the end of the first liquid containerthat attaches to the first connector of the component. In addition, thecomponent may include a second connector, such as screw threads, on theend of the component that attaches to the second liquid container, andthe second liquid container may include a corresponding connector, suchas corresponding screw threads, on the end of the second liquidcontainer that attaches to the second connector of the component.

As described above, the membrane component may be configured as a flowpath through which a volume of a fluid (e.g., gas or liquid) can flowthrough as the fluid traverses from the first liquid container to thesecond liquid container or from the second liquid container to the firstliquid container. For example, the membrane component may be configuredas a flow path for a liquid, such as a suspension of liposomes. The sizeof the membrane component, and thus the interior volume of the membranecomponent may range from 0.1 ml to 1000 ml, such as from 0.1 ml to 900ml, or 0.1 ml to 800 ml, or 0.1 ml to 700 ml, or 0.1 ml to 600 ml, or0.1 ml to 500 ml, or 0.1 ml to 400 ml, or 0.1 ml to 300 ml, or 0.1 ml to200 ml, or 0.1 ml to 100 ml, or 0.1 ml to 50 ml, or 0.1 ml to 25 ml, or0.1 ml to 10 ml, or 0.1 ml to 5 ml, or 0.1 ml to 2 ml, or 0.1 ml to 1.5ml, or 0.1 ml to 1 ml, or 0.1 ml to 0.5 ml. In certain instances, themembrane component is configured to have an interior volume ranging from0.1 ml to 5 ml, such as, for example, 0.5 ml, or 1 ml, or 1.5 ml, or 2ml. In other instances, the membrane component is configured to have aninterior volume ranging from 0.1 ml to 100 ml, such as 50 ml, or 25 ml.

In certain embodiments, the membrane component has a width (which mayalso be referred to as the diameter for cylindrical membrane components)that is the same or substantially the same as the width or diameter ofthe first liquid container and/or the second liquid container. Forinstance, the membrane component may have an inner diameter the same orsubstantially the same as an inner diameter of the first liquidcontainer and/or the second liquid container. In some cases, themembrane component has a width (or diameter) ranging from 0.5 cm to 5cm, such as 0.5 cm to 4.5 cm, or 0.5 cm to 4 cm, or 0.5 cm to 3.5 cm, or0.5 cm to 3 cm, or 0.5 cm to 2.5 cm, or 0.5 cm to 2 cm, or 0.5 cm to 1.5cm, or 0.5 cm to 1 cm. In some instances, the membrane component has awidth (or diameter) ranging from 0.5 cm to 2.5 cm. In some instances,the membrane component has a width (or diameter) ranging from 0.5 cm to1 cm. In certain embodiments, the membrane component has a lengthranging from 1 cm to 20 cm, such as 1 cm to 15 cm, or 1 cm to 10 cm, or1 cm to 5 cm, or 1 cm to 2.5 cm. In some instances, the membranecomponent has a length ranging from 1 cm to 10 cm. In some instances,the membrane component has a length ranging from 1 cm to 5 cm. In someinstances, the membrane component has a length ranging from 1 cm to 2.5cm.

Embodiments of the membrane component can be compatible with the liquidand/or liposomes or other ingredients that may be in contact with themembrane component. Examples of suitable membrane component materialsfor the liposome extrusion devices include, but are not limited to,plastics, such as polypropylene, polymethylpentene,polytetrafluoroethylene (PTFE), perfluoroethers (PFE), fluorinatedethylene propylene (FEP), perfluoroalkoxy alkanes (PFA), polyethyleneterephthalate (PET), polyethylene (PE), polyetheretherketone (PEEK), andthe like.

As discussed above, in certain embodiments, the membrane component isconfigured to position the membrane between a first liquid container anda second liquid container. As such, in some instances, the liposomeextrusion device includes the first liquid container and the secondliquid container. Embodiments of the subject liquid containers may beconfigured to contain a volume of a liquid (e.g., a suspension ofliposomes and/or population of liposomes). In some instances, thesubject liquid container includes a first end and a second end opposingthe first end. In some embodiments, the first end includes an opening.In these instances, the opening in the liquid container exposes theinterior of the liquid container to the surrounding environment, e.g.,such that the contents of the liquid container are under the sameatmospheric pressure as the surrounding environment. For example, theopening may be used to allow access to the interior of the liquidcontainer, such as for introducing a suspension of liposomes into theliquid container or removing a suspension of liposomes from the liquidcontainer. In certain instances, the membrane component is removablefrom the first and/or second liquid container, such that after applyinga centrifugal force in a manner sufficient to pass the liposomes throughthe membrane, the membrane component may be removed from the firstand/or second liquid container. In these instances, a removable membranecomponent allows access to the liposomes that have passed through themembrane. These liposomes may be collected and analyzed or used insubsequent procedures.

In some instances, the liquid container (e.g., the first and/or secondliquid container) includes a closed end opposite from the open end ofthe liquid container. As such, the liquid container may be configured tocontain a volume of liquid as described above. The size of the liquidcontainer may depend on the volume of liquid to be held in the liquidcontainer. For instance, the liquid container may be configured to holda volume (e.g., a volume of a liquid) ranging from 0.1 ml to 1000 ml,such as from 0.1 ml to 900 ml, or 0.1 ml to 800 ml, or 0.1 ml to 700 ml,or 0.1 ml to 600 ml, or 0.1 ml to 500 ml, or 0.1 ml to 400 ml, or 0.1 mlto 300 ml, or 0.1 ml to 200 ml, or 0.1 ml to 100 ml, or 0.1 ml to 50 ml,or 0.1 ml to 25 ml, or 0.1 ml to 10 ml, or 0.1 ml to 5 ml, or 0.1 ml to2 ml, or 0.1 ml to 1.5 ml, or 0.1 ml to 1 ml, or 0.1 ml to 0.5 ml. Incertain instances, the liquid container is configured to hold a volumeranging from 0.1 ml to 5 ml, such as, for example, 0.5 ml, or 1 ml, or1.5 ml, or 2 ml. In other instances, the liquid container is configuredto hold a volume ranging from 0.1 ml to 100 ml, such as 50 ml, or 25 ml.The liquid container (e.g., the first and/or second liquid container)may further include one or more side walls, which form the sides of theliquid container between the opening at the first end of the liquidcontainer and the closed second end of the liquid container. In certainembodiments, the liquid container is in the shape of a cylinder, wherethe cylinder has an opening at a first end and a closed second opposingend of the cylinder. In some cases, the liquid container has a circularcross section. The shape of the liquid container may vary and may dependon the use of the liposome extrusion device. For example, the liquidcontainer may be configured in a shape that is compatible with themethods of the present disclosure. For instance, the liquid containermay be configured in a shape compatible with typical laboratoryequipment used to perform the method, such as a shape compatible with acentrifuge. As described above, the liquid container may be configuredto hold a volume of a liquid. In these embodiments, the liquid containermay be a vial or a test tube. In certain cases, the liquid container isa vial. In certain cases, the liquid container is a test tube. Examplesof suitable liquid containers include, but are not limited to,centrifuge tubes, microcentrifuge tubes, Eppendorf® tubes, and the like.

In certain embodiments, the liquid container (e.g., the first and/orsecond liquid container) has a width (which may also be referred to asthe diameter for cylindrical liquid containers) ranging from 0.5 cm to 5cm, such as 0.5 cm to 4.5 cm, or 0.5 cm to 4 cm, or 0.5 cm to 3.5 cm, or0.5 cm to 3 cm, or 0.5 cm to 2.5 cm, or 0.5 cm to 2 cm, or 0.5 cm to 1.5cm, or 0.5 cm to 1 cm. In some instances, the liquid container has awidth (or diameter) ranging from 0.5 cm to 2.5 cm. In some instances,the liquid container has a width (or diameter) ranging from 0.5 cm to 1cm. In certain embodiments, the liquid container has a length rangingfrom 1 cm to 20 cm, such as 1 cm to 15 cm, or 1 cm to 10 cm, or 1 cm to5 cm, or 1 cm to 2.5 cm. In some instances, the liquid container has alength ranging from 1 cm to 10 cm. In some instances, the liquidcontainer has a length ranging from 1 cm to 5 cm. In some instances, theliquid container has a length ranging from 1 cm to 2.5 cm.

Embodiments of the liquid container (e.g., the first and/or secondliquid container) can be compatible with the liquid and/or liposomes orother ingredients that may be in contact with the liquid container.Examples of suitable liquid container materials for the liposomeextrusion devices include, but are not limited to, plastics, such aspolypropylene, polymethylpentene, polytetrafluoroethylene (PTFE),perfluoroethers (PFE), fluorinated ethylene propylene (FEP),perfluoroalkoxy alkanes (PFA), polyethylene terephthalate (PET),polyethylene (PE), polyetheretherketone (PEEK), and the like.

In some embodiments, as described above, the liquid container (e.g., thefirst and/or second liquid container) is configured as a container,where the container is configured to hold a certain volume of a liquid.In some embodiments, the liquid container may be a sealable container.That is, the liquid container may include a seal or a sealable surfacethat substantially prevents the contents of the liquid container (e.g.,liquid inside the liquid container) from exiting the liquid container.The seal or sealable surface of the liquid container may alsosubstantially prevent other substances from entering the liquidcontainer. For example, the seal or sealable surface may be aliquid-tight, such as a water-tight, seal that substantially preventsliquids, such as water or aqueous solutions or suspensions, fromentering or exiting the liquid container, or may be a gas-tight seal,such as an air-tight seal, that substantially prevents gases, such asair, from entering or exiting the liquid container. In some instances,the seal or sealable surface can be unsealed, such that the contents ofthe liquid container may be exposed to the surrounding environment whenso desired, e.g., if it is desired to remove a portion of the contentsof the liquid container.

In certain embodiments, the liquid container (e.g., the first and/orsecond liquid container) includes a sealable surface as described above.The sealable surface may be present on a surface at an open end of theliquid container. For instance, the sealable surface of the liquidcontainer may be a surface on the open end of the liquid container thatinterfaces with a corresponding seal or sealable surface on the membranecomponent. In some cases, connection of the liquid container to themembrane component causes the sealable surface of the liquid containerto contact and seal against the corresponding seal or sealable surfaceof the membrane component, thus creating a liquid-tight and/or gas-tightseal between the liquid container and the membrane component. As such,an interior of the liposome extrusion device may be sealed from thesurrounding atmosphere. For example, when the membrane component isattached to the first liquid container and the second liquid container,the interior of the first liquid container, the interior of the secondliquid container and the interior of the membrane component may besealed from the surrounding atmosphere. In some cases, when the membranecomponent is attached to the first liquid container and the secondliquid container, the interior of the first liquid container is sealedfrom the surrounding atmosphere. In some cases, when the membranecomponent is attached to the first liquid container and the secondliquid container, the interior of the second liquid container is sealedfrom the surrounding atmosphere. In some cases, when the membranecomponent is attached to the first liquid container and the secondliquid container, the interior of the membrane component is sealed fromthe surrounding atmosphere.

In some instances, the seal is made of a resilient material to provide abarrier (e.g., liquid-tight seal and/or gas-tight seal) for retainingthe contents of the liquid container inside the liquid container.Particular types of seals include, but are not limited to, films, suchas polymer films, caps, etc., depending on the type of container.Suitable materials for the seal include, for example, rubber or polymerseals, such as, but not limited to, silicone rubber, natural rubber,styrene butadiene rubber, ethylene-propylene copolymers,polychloroprene, polyacrylate, polybutadiene, polyurethane, styrenebutadiene, and the like, and combinations thereof. The seal may bepresent at the open end of the liquid container that interfaces with acorresponding seal or sealable surface on the membrane component. Insome cases, connection of the liquid container to the membrane componentcauses the seal of the liquid container to contact and seal against thecorresponding seal or sealable surface of the membrane component, thuscreating a liquid-tight and/or gas-tight seal between the liquidcontainer and the membrane component. In some cases, the seal is in theshape of an O-ring having a diameter the same or substantially the sameas the diameter of the liquid container and/or the membrane component.As such, an interior of the liposome extrusion device may be sealed fromthe surrounding atmosphere. For example, when the membrane component isattached to the first liquid container and the second liquid container,the interior of the first liquid container, the interior of the secondliquid container and the interior of the membrane component may besealed from the surrounding atmosphere.

As described above, certain embodiments of the liposome extrusion deviceinclude a porous membrane that includes one or more layers of a membranematerial as described herein. The liposome extrusion device may alsoinclude a component configured to position the membrane between thefirst liquid container and the second liquid container.

An example of a liposome extrusion device according to embodiments ofthe present disclosure is shown in FIG. 1. In FIG. 1, the liposomeextrusion device 5 is shown in four views: FIG. 1, panel A, shows anexploded perspective view of the liposome extrusion device; FIG. 1,panel B, shows an exploded cross-sectional view of the liposomeextrusion device; FIG. 1, panel C, shown a perspective view of anassembled liposome extrusion device; and FIG. 1, panel D, shows across-sectional view of the assembled liposome extrusion device. In FIG.1, the liposome extrusion device 5 is configured as a vial. The liposomeextrusion device 5 includes a first liquid container 10 in the form of avial (e.g., an Eppendorf tube), and a second liquid container 30, whichis also in the form of a vial (e.g., an Eppendorf tube). The liposomeextrusion device 5 also includes a membrane component 20, which has afirst subcomponent 21 and a second subcomponent 23. The membranecomponent 20 also includes a porous membrane 22 positioned at aninterface between the first subcomponent 21 and the second subcomponent23. As shown in FIG. 1, assembly of the liposome extrusion device 5 canbe performed by positioning the membrane 22 between the firstsubcomponent 21 and the second subcomponent 23 and attaching the firstsubcomponent 21 and the second subcomponent 23 together, such that themembrane 22 is held in position between the first subcomponent 21 andthe second subcomponent 23. Either one, or both, the first liquidcontainer 10 or second liquid container 30 can be loaded with asuspension of liposomes, and then the first liquid container 10 and thesecond liquid container 30 can be connected to the membrane component 20at opposing ends of the membrane component 20.

After the liposome extrusion device is assembled, the liposome extrusiondevice may then be placed in a centrifuge. The centrifuge may beoperated (e.g., by spinning) to apply a centrifugal force to theliposome extrusion device such that the suspension of liposomes from oneof the liquid containers passes through the porous membrane 20 and intothe opposing liquid container. Extrusion of the liposomes through thepores of the membrane may produce a population of liposomes having adefined size, as described herein.

Systems

Systems of the present disclosure include a liposome extrusion device asdescribed herein. For example, the liposome extrusion device may includea porous membrane and a component (e.g., membrane component) configuredto position the membrane between a first liquid container and a secondliquid container. As described herein, when the component is attached tothe first liquid container and the second liquid container, an interiorof the component may be sealed from the surrounding atmosphere. Inaddition, systems of the present disclosure may also include the firstliquid container and the second liquid container, as described herein.

In certain embodiments, the liposome extrusion device includes asuspension of liposomes. For example, during use of the liposomeextrusion device, a suspension of heterogeneous liposomes may beintroduced into either, or both, the first liquid container or thesecond liquid container. As described herein, a centrifugal force maythen be applied to the suspension of liposomes such that the liposomespass through the porous membrane to produce a population of liposomes,such as a population of liposomes having a defined size. As such,certain embodiments of the systems of the present disclosure may alsoinclude a centrifuge. Centrifuges suitable for use in the subjectsystems include any of the various types of centrifuges. For example, asuitable centrifuge may include a centrifuge configured to apply acentrifugal force to the suspension of liposomes, which may include acentrifuge configured to apply a centrifugal force sufficient to causethe liposomes to pass through the pores of the membrane. In some cases,the centrifuge is configured to apply a centrifugal force greater thanstandard gravity, such as for example 2 g or more, or 5 g or more, or 10g or more, or 25 g or more, or 50 g or more, or 100 g or more, or 250 gor more, or 500 g or more, or 750 g or more, or 1000 g or more, or 1500g or more, or 2000 g or more, or 2500 g or more, or 3000 g or more, or3500 g or more, or 4000 g or more, or 4500 g or more, or 5000 g or more,or 5500 g or more, or 6000 g or more, or 6500 g or more, or 7000 g ormore, or 7500 g or more, or 8000 g or more, or 8500 g or more, or 9000 gor more, or 9500 g or more, or 10,000 g or more, or 15,000 g or more, or20,000 g or more, or 25,000 g or more, where in some instances the forceis 30,000 g or less, such as 27,500 g or less. In some cases, thecentrifuge is configured to apply a centrifugal force by spinning at 10rpm or more, such as 50 rpm or more, or 100 rpm or more, or 250 rpm ormore, or 500 rpm or more, or 750 rpm or more, or 1000 rpm or more, or1500 rpm or more, or 2000 rpm or more, or 2500 rpm or more, or 3000 rpmor more, or 3500 rpm or more, or 4000 rpm or more, or 4500 rpm or more,or 5000 rpm or more, or 5500 rpm or more, or 6000 rpm or more, or 6500rpm or more, or 7000 rpm or more, or 7500 rpm or more, or 8000 rpm ormore, or 8500 rpm or more, or 9000 rpm or more, or 9500 rpm or more, or10,000 rpm or more.

As described above, a centrifugal force may be applied to the suspensionof liposomes using a centrifuge. As such, the liposome extrusion devicemay be inserted into a centrifuge in order to apply the centrifugalforce to a suspension of liposomes contained in the liposome extrusiondevice. For example, the liposome extrusion device may be inserted intoa centrifuge tube holder of the centrifuge, and the liposome extrusiondevice may be held in the centrifuge tube holder while the centrifugalforce is applied, such as by spinning the centrifuge. In certainembodiments, the system includes an adapter configured to contain theliposome extrusion device. The adapter may facilitate insertion andretention of the liposome extrusion device in the centrifuge. Forinstance, the adapter may facilitate insertion and retention of theliposome extrusion device in the centrifuge tube holder of thecentrifuge. In some instances, the centrifuge tube holder may have acircular cross-section; i.e., the centrifuge tube holder may be in theshape of a cylinder. In some cases, the adapter is also in the shape ofa cylinder. For example, the adapter may be configured as a cylinderwith an outer surface concentric to an interior surface of thecentrifuge tube holder of the centrifuge. The liposome extrusion devicemay be held within an interior of the adapter. In some instances, aninterior surface of the adapter is configured to hold the liposomeextrusion device such that the liposome extrusion device does notsubstantially change position inside the adapter. For example, theposition of the liposome extrusion device within the adapter may notsubstantially change during use, such as when the centrifugal force isapplied. As such, in certain cases, an interior surface of the adapterhas a shape that substantially conforms to an outer surface of theliposome extrusion device. In certain instances, the adapter may beprovided in two or more sections or pieces. The interior of the adaptermay be exposed by separating the two sections of the adapter, thusallowing the liposome extrusion device to be inserted or removed fromthe adapter. As such, the two sections of the adapter are removablyattached to each other. As described above, the adapter may be in theshape of a cylinder, and as such, in some cases, the adapter is providedin two longitudinal sections, where the adapter is divided into the twolongitudinal sections by a plane along the longitudinal axis of theadapter. The dimensions of the adaptor may vary, as desired. In certaininstances, the adapter may have a length ranging from 100 to 150 mm. Insome embodiments, the adapter may have a width, e.g., a diameter wherethe adaptor is configured as a cylinder, ranging from 10 to 35 mm. Theadapter may have any outer configuration or shape which is dimensionedso that the adaptor may be accommodated by a holder of a centrifugedevice, such that the adaptor can be stably positioned in a holder of acentrifuge device, e.g., as illustrated in the embodiment shown in FIG.2, described below.

An example of a system for producing a population of liposomes accordingto embodiments of the present disclosure is shown in FIG. 2. As shown inFIG. 2, the system includes a liposome extrusion device 5, as describedherein. The liposome extrusion device is inserted into an adapter 40,which facilitates insertion and retention of the liposome extrusiondevice in a centrifuge 50. The liposome extrusion device 5, which iscontained in the adapter 40, is inserted into a centrifuge tube holderof the centrifuge 50 and a centrifugal force is applied by spinning thecentrifuge. In the embodiment illustrated in FIG. 2, the suspension ofliposomes in contained in liquid container A of the liposome extrusiondevice 5. When applying the centrifugal force, the liposome extrusiondevice 5 is positioned in the centrifuge 50 such that the liquidcontainer containing the suspension of liposomes A is positionedproximal (e.g., closer) to the axis of rotation of the centrifuge 50 andthe opposing liquid container B is positioned distal (e.g., furtheraway) from the axis of rotation. For example, as shown in FIG. 2, liquidcontainer A is positioned at the top and liquid container B ispositioned at the bottom of the centrifuge tube holder. When thecentrifugal force is applied, the suspension of liposomes traverses fromthe liquid container A to the liquid container B such that thesuspension of liposomes is extruded from the liquid container A into theliquid container B through the membrane (see Step I in FIG. 2). Asdescribed herein, the centrifugal force may be applied repeated times.As such, the liposome extrusion device may be inverted after applyingthe centrifugal force and before applying the next centrifugal force. Asshown in FIG. 2 (see Step II), inverting the position of the liposomeextrusion device in the centrifuge may be accomplished by removing theliposome extrusion device from the centrifuge and inserting the liposomeextrusion device back into the centrifuge in an orientation oppositefrom the orientation of the liposome extrusion device before theliposome extrusion device was removed from the centrifuge. For instance,after applying the first centrifugal force as described above, thesuspension of liposomes in now contained in liquid container B. Theliposome extrusion device may be inverted such that liquid container Bis positioned proximal (e.g., closer) to the axis of rotation of thecentrifuge and the liquid container A is positioned distal (e.g.,further away) from the axis of rotation of the centrifuge. For example,as shown in FIG. 2 (Step II), liquid container B is positioned at thetop and liquid container A is positioned at the bottom of the centrifugetube holder. Upon application of the centrifugal force, as describedabove, the suspension of liposomes traverses from liquid container B toliquid container A such that the suspension of liposomes is extrudedfrom liquid container B into liquid container A through the membrane.Repeated alternations of applying the centrifugal force and invertingthe liposome extrusion device in the centrifuge can be performed toproduce a desired population of liposomes (e.g., a population ofliposomes having a defined size).

Kits

Aspects of the disclosure also include kits that include a subjectliposome extrusion device (e.g., a porous membrane and a component(membrane component) as described herein). In certain embodiments, thekit includes a subject liposome extrusion device and a packagingconfigured to hold the liposome extrusion device. The packaging may be asealed packaging, e.g., a water-resistant and/or water vapor-resistantcontainer, optionally under a gas-tight and/or vacuum seal. In certaininstances, the packaging is a sterile packaging, configured to maintainthe device enclosed in the packaging in a sterile environment. By“sterile” is meant that there are substantially no microbes (such asfungi, bacteria, viruses, spore forms, etc.).

In some instances, the kit may also include a first liquid container,such as a centrifuge tube, as described herein. In some instances, thekit may also include a second liquid container, such as a centrifugetube, as described herein. In some instances, the kit may also includean adapter configured to contain the liposome extrusion device, asdescribed herein.

The kits may further include a liquid. For instance, the kit may includea buffer, such as a sample buffer, a wash buffer, an assay buffer, andthe like. In some cases, the kit may include a liquid suitable for asuspension of liposomes. The kits may further include additionalreagents, such as but not limited to, detectable labels (e.g.,fluorescent labels, colorimetric labels, chemiluminescent labels,multicolor reagents, avidin-streptavidin associated detection reagents,radiolabels, gold particles, magnetic labels, etc.), and the like.

In certain embodiments, the kits may also include a calibrationstandard. For example, the kits may include a set of labelled beads,such as a set of standard fluorescently labelled beads. The calibrationstandard may be useful for determining the accuracy of the assayapparatus and for ensuring consistency between subsequent assays. Forexample, the calibration standard may be useful for determining theaccuracy of a flow cytometer. In some cases, the calibration standardincludes a labelled bead, such as a fluorescently labelled bead. Thefluorescently labelled bead may be a standard fluorescently labeled beadthat is typically used as a calibration standard. Examples of standardfluorescently labeled beads include, but are not limited to,fluorescently labelled microparticles or nanoparticles. In some cases,the fluorescently labeled beads are configured such that they remainsuspended in the assay mixture and do not substantially settle oraggregate. In some embodiments, the fluorescently labeled beads include,but are not limited to, fluorescently labelled polystyrene beads,fluorescein beads, rhodamine beads, and other beads tagged with afluorescent dye. Additional examples of fluorescently labeled beads aredescribed in U.S. Pat. Nos. 6,350,619; 7,738,094; and 8,248,597, thedisclosures of each of which are herein incorporated by reference intheir entirety.

In addition to the above components, the subject kits may furtherinclude instructions for practicing the subject methods. Theseinstructions may be present in the subject kits in a variety of forms,one or more of which may be present in the kit. One form in which theseinstructions may be present is as printed information on a suitablemedium or substrate, e.g., a piece or pieces of paper on which theinformation is printed, in the packaging of the kit, in a packageinsert, etc. Another form would be a computer readable medium, e.g., CD,DVD, Blu-Ray, computer-readable memory (e.g., flash memory), etc., onwhich the information has been recorded or stored. Yet another form thatmay be present is a website address which may be used via the Internetto access the information at a removed site. Any convenient form ofinstructions may be present in the kits.

Utility

The subject methods, devices and systems find use in applications wherea population of liposomes of defined size may be desired for research orlaboratory testing. In some embodiments, the subject methods, devicesand systems facilitate the accurate analysis of analytes (e.g., cells)obtained from a biological sample (e.g., organ, tissue, tissue fragment,fluid). In certain instances, the subject methods, devices and systemsfind use in testing the accuracy of an apparatus used for the analysisof such analytes for research or laboratory testing. For example, thesubject methods, devices and systems find use in testing the accuracy ofa flow cytometer. In some cases, the population of liposomes producedusing the methods, devices and systems of the present disclosure areused as a calibration standard for an apparatus, such as a flowcytometer. Thus, the subject methods, devices and systems find use inthe efficient preparation of a population of liposomes from a suspensionof heterogeneous liposomes.

In addition, the subject methods, devices and systems find use in thepreparation of a population of liposomes without the need forspecialized liposome extrusion systems, such as liposome extrusionsystems that require syringes or gas/liquid handling components forapplying increased pressure or a vacuum on a suspension of liposomes toforce the liposomes through an extrusion membrane. In some instances,the subject methods, devices and systems find use in the production of apopulation of liposomes using standard laboratory equipment at standardatmospheric pressure. Stated another way, the subject methods, devicesand systems find use in the production of a population of liposomeswithout the application of an increased pressure or a vacuum on asuspension of liposomes.

The subject methods, devices and systems also find use in thepreparation of a population of liposomes without the need for openingthe liposome extrusion device or exposing the suspension of liposomes tothe surrounding atmosphere during the (repeated) centrifugation process,since the liposome extrusion device can be inverted between eachapplication of a centrifugal force. As such, the subject methods,devices and systems facilitate the preparation of a population ofliposomes with significantly less or substantially no contamination fromcontaminants from the surrounding atmosphere or outside environment. Inaddition, in the event that liposome precipitate forms on the bottom ofa liquid container of the liposome extrusion device, the subjectmethods, devices and systems provide for re-suspension of theprecipitate by vortexing the liposome extrusion device without the needto open the liposome extrusion device and expose the contents of theliposome extrusion device to the surrounding environment.

As can be appreciated from the disclosure provided above, embodiments ofthe present disclosure have a wide variety of applications. Accordingly,the examples presented herein are offered for illustration purposes andare not intended to be construed as a limitation on the embodiments ofthe present disclosure in any way. Those of ordinary skill in the artwill readily recognize a variety of noncritical parameters that could bechanged or modified to yield essentially similar results. Thus, thefollowing examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how tomake and use embodiments of the present disclosure, and are not intendedto limit the scope of what the inventors regard as their invention norare they intended to represent that the experiments below are all or theonly experiments performed. Efforts have been made to ensure accuracywith respect to numbers used (e.g. amounts, temperature, etc.) but someexperimental errors and deviations should be accounted for. Unlessindicated otherwise, parts are parts by weight, molecular weight isweight average molecular weight, temperature is in degrees Celsius, andpressure is at or near atmospheric.

The subject methods, devices and systems find use in the preparation ofa population of liposomes for therapeutic applications, such asliposomes that contain a substance, e.g., a drug, a protein, afluorescent compound, etc., which can be used to deliver the substanceto a target area in a subject. For example, the subject methods, devicesand systems fid use in the preparation of a population of liposomes fordrug delivery, cell therapy and in vivo applications, as well asanalytical applications, such as for immune analysis.

EXAMPLES Example 1

Experiments are performed to produce a population of liposomes accordingto embodiments of the present disclosure. A dry lipid mixture isprepared by lyophilization or drying under a stream of inert gas,followed by desiccation by vacuum. The dry lipids are hydrated with anaqueous solution (e.g., a buffered saline solution) for 30-60 min. Forlipids with a high phase transition temperature, the aqueous solution ispre-warmed before being added to the dry lipids. If desired, thehydrated lipid suspension can be subjected to one or more freeze/thawcycles, e.g., 3 to 5 freeze/thaw cycles, to increase the efficiency ofentrapment of water-soluble compounds. For lipids with a high phasetransition temperature, the liposome extrusion device is pre-warmed in athermostatic device, if necessary. After the dry lipids are hydratedwith an aqueous solution, a sample of the aqueous suspension is loadedinto a liquid container of the liposome extrusion device. The liposomeextrusion device is placed in the rotor of the centrifuge with thesample-loaded liquid container on top. The sample is centrifuged. Thecentrifugation time and speed (rpm) is varied depending on the type ofmembrane being used. The centrifugation is repeated if necessary,inverting the liposome extrusion device between each centrifugation ofthe sample by removing the liposome extrusion device from the rotor ofthe centrifuge, turning it over, and placing the liposome extrusiondevice back in the rotor. The sample-loaded liquid container is on topagain, and the sample is centrifuged. The centrifugation is repeatedwith inversion of the liposome extrusion device as many times asnecessary to produce a population of liposomes of a desired definedsize.

EMBODIMENTS

The disclosure set forth herein is also defined by the followingclauses:

1. A method for producing a uniform population of liposomes, the methodcomprising:

introducing a suspension of liposomes into a liposome extrusion devicecomprising:

-   -   a first liquid container;    -   a second liquid container in fluid communication with the first        liquid container;    -   a porous membrane; and    -   a component configured to position the membrane between the        first liquid container and the second liquid container; and

applying a centrifugal force to the suspension of liposomes in a mannersufficient to pass the liposomes through the membrane to produce auniform population of liposomes.

2. The method according to Clause 1, wherein the introducing comprisesintroducing the suspension of liposomes into the first liquid containeror the second liquid container.3. The method according to Clause 2, further comprising connecting theliquid container containing the suspension of liposomes to thecomponent.4. The method according to Clause 3, further comprising connecting theother liquid container to the component.5. The method according to any of Clauses 1 to 4, wherein the applyingthe centrifugal force is repeated one or more times.6. The method according to Clause 5, further comprising inverting theliposome extrusion device between each repetition of the applying.7. The method according to any of Clauses 1 to 6, wherein the applyingthe centrifugal force comprises spinning the liposome extrusion devicein a centrifuge.8. The method according to any of Clauses 1 to 7, wherein the applyingcomprises applying the centrifugal force such that the suspension ofliposomes is extruded from the first liquid container into the secondliquid container through the membrane, or wherein the applying comprisesapplying the centrifugal force such that the suspension of liposomes isextruded from the second liquid container into the first liquidcontainer through the membrane.9. The method according to any of Clauses 1 to 8, wherein the applyingthe centrifugal force is performed at atmospheric pressure.10. The method according to any of Clauses 1 to 9, wherein the firstliquid container comprises a centrifuge tube.11. The method according to any of Clauses 1 to 10, wherein the secondliquid container comprises a centrifuge tube.12. The method according to any of Clauses 1 to 11, wherein thecomponent comprises a first connector for connecting the component tothe first liquid container.13. The method according to Clause 12, wherein the first connectorcomprises screw threads and an open end of the first liquid containercomprises corresponding screw threads.14. The method according to any of Clauses 1 to 13, wherein thecomponent comprises a second connector for connecting the component tothe second liquid container.15. The method according to Clause 14, wherein the second connectorcomprises screw threads and an open end of the second liquid containercomprises corresponding screw threads.16. The method according to any of Clauses 1 to 15, wherein the membraneis positioned between a first end of the component and a second end ofthe component.17. The method according to any of Clauses 1 to 16, wherein thecomponent comprises a first subcomponent and a second subcomponentremovably attached to the first subcomponent.18. The method according to Clause 17, wherein the membrane ispositioned at an interface between the first subcomponent and the secondsubcomponent.19. The method according to any of Clauses 1 to 18, wherein thecomponent has an inner diameter the same as an inner diameter of thefirst liquid container or the second liquid container.20. The method according to any of Clauses 1 to 19, wherein the membranehas a pore size of 1000 nm or less.21. The method according to any of Clauses 1 to 20, wherein the membranehas a pore size of 500 nm or less.22. The method according to any of Clauses 1 to 21, wherein the membranehas a pore size of 250 nm or less.23. The method according to any of Clauses 1 to 22, wherein the membranecomprises one or more layers of a membrane material.24. The method according to Clause 23, wherein the membrane materialcomprises a polymer.25. The method according to Clause 24, wherein the polymer comprisespolycarbonate.26. The method according to any of Clauses 23 to 25, wherein themembrane comprises two or more layers of a membrane material.27. The method according to Clause 26, wherein the pore size of each ofthe two or more layers of the membrane material is the same.28. The method according to Clause 26, wherein the pore size of at leasttwo of the two or more layers of the membrane material are different.29. The method according to any of Clauses 1 to 28, further comprisingpreparing the suspension of liposomes.30. The method according to any of Clauses 1 to 29, wherein thesuspension of liposomes comprises a population of liposomes havingheterogeneous sizes.31. The method according to any of Clauses 1 to 30, wherein theliposomes comprise a fluorescent label.32. The method according to any of Clauses 1 to 31, wherein the uniformpopulation of liposomes has an average diameter of 1000 nm or less.33. The method according to any of Clauses 1 to 32, wherein the uniformpopulation of liposomes has an average diameter of 500 nm or less.34. The method according to any of Clauses 1 to 33, wherein the uniformpopulation of liposomes has an average diameter of 250 nm or less.35. A liposome extrusion device comprising:

a porous membrane; and

a component configured to position the membrane between a first liquidcontainer and a second liquid container, wherein, when the component isattached to the first liquid container and the second liquid container,an interior of the component is sealed from the surrounding atmosphere.

36. The device according to Clause 35, further comprising the firstliquid container.37. The device according to Clause 35 or 36, further comprising thesecond liquid container.38. The device according to any of Clauses 35 to 37, wherein the firstliquid container comprises a centrifuge tube.39. The device according to any of Clauses 35 to 38, wherein the secondliquid container comprises a centrifuge tube.40. The device according to any of Clauses 35 to 39, wherein thecomponent comprises a first connector for connecting the component tothe first liquid container.41. The device according to Clause 40, wherein the first connectorcomprises screw threads and an open end of the first liquid containercomprises corresponding screw threads.42. The device according to any of Clauses 35 to 41, wherein thecomponent comprises a second connector for connecting the component tothe second liquid container.43. The device according to Clause 42, wherein the second connectorcomprises screw threads and an open end of the second liquid containercomprises corresponding screw threads.44. The device according to any of Clauses 35 to 43, wherein themembrane is positioned between a first end of the component and a secondend of the component.45. The device according to any of Clauses 35 to 44, wherein thecomponent comprises a first subcomponent and a second subcomponentremovably attached to the first subcomponent.46. The device according to Clause 45, wherein the membrane ispositioned at an interface between the first subcomponent and the secondsubcomponent.47. The device according to any of Clauses 35 to 46, wherein thecomponent has an inner diameter the same as an inner diameter of thefirst liquid container or the second liquid container.48. The device according to any of Clauses 35 to 47, wherein themembrane has a pore size of 1000 nm or less.49. The device according to any of Clauses 35 to 48, wherein themembrane has a pore size of 500 nm or less.50. The device according to any of Clauses 35 to 49, wherein themembrane has a pore size of 250 nm or less.51. The device according to any of Clauses 35 to 50, wherein themembrane comprises one or more layers of a membrane material.52. The device according to Clause 51, wherein the membrane materialcomprises a polymer.53. The device according to Clause 52, wherein the polymer comprisespolycarbonate.54. The device according to Clause 35 to 53, wherein the membranecomprises two or more layers of a membrane material.55. The device according to Clause 54, wherein the pore size of each ofthe two or more layers of the membrane material is the same.56. The device according to Clause 54, wherein the pore size of at leasttwo of the two or more layers of the membrane material are different.57. A system for producing a uniform population of liposomes, the systemcomprising:

a first liquid container;

a second liquid container; and

a liposome extrusion device comprising:

-   -   a porous membrane; and    -   a component configured to position the membrane between the        first liquid container and the second liquid container, wherein,        when the component is attached to the first liquid container and        the second liquid container, an interior of the component is        sealed from the surrounding atmosphere.        58. The system according to Clause 57, further comprising an        adapter configured to contain the liposome extrusion device.        59. The system according to Clause 58, wherein the adapter        comprises a cylinder with an outer surface concentric to an        interior surface of a centrifuge tube holder of a centrifuge.        60. The system according to any of Clauses 57 to 59, wherein the        liposome extrusion device contains a suspension of liposomes.        61. The system according to any of Clauses 57 to 60, further        comprising a centrifuge.        62. The system according to any of Clauses 57 to 61, wherein the        first liquid container comprises a centrifuge tube.        63. The system according to any of Clauses 57 to 62, wherein the        second liquid container comprises a centrifuge tube.        64. The system according to any of Clauses 57 to 63, wherein the        first liquid container comprises a centrifuge tube.        65. The system according to any of Clauses 57 to 64, wherein the        second liquid container comprises a centrifuge tube.        66. The system according to any of Clauses 57 to 65, wherein the        component comprises a first connector for connecting the        component to the first liquid container.        67. The system according to Clause 66, wherein the first        connector comprises screw threads and an open end of the first        liquid container comprises corresponding screw threads.        68. The system according to any of Clauses 57 to 67, wherein the        component comprises a second connector for connecting the        component to the second liquid container.        69. The system according to Clause 68, wherein the second        connector comprises screw threads and an open end of the second        liquid container comprises corresponding screw threads.        70. The system according to any of Clauses 57 to 69, wherein the        membrane is positioned between a first end of the component and        a second end of the component.        71. The system according to any of Clauses 57 to 70, wherein the        component comprises a first subcomponent and a second        subcomponent removably attached to the first subcomponent.        72. The system according to Clause 71, wherein the membrane is        positioned at an interface between the first subcomponent and        the second subcomponent.        73. The system according to any of Clauses 57 to 72, wherein the        component has an inner diameter the same as an inner diameter of        the first liquid container or the second liquid container.        74. The system according to any of Clauses 57 to 73, wherein the        membrane has a pore size of 1000 nm or less.        75. The system according to any of Clauses 57 to 74, wherein the        membrane has a pore size of 500 nm or less.        76. The system according to any of Clauses 57 to 75, wherein the        membrane has a pore size of 250 nm or less.        77. The system according to any of Clauses 57 to 76, wherein the        membrane comprises one or more layers of a membrane material.        78. The system according to Clause 77, wherein the membrane        material comprises a polymer.        79. The system according to Clause 78, wherein the polymer        comprises polycarbonate.        80. The system according to Clause 57 to 79, wherein the        membrane comprises two or more layers of a membrane material.        81. The system according to Clause 80, wherein the pore size of        each of the two or more layers of the membrane material is the        same.        82. The system according to Clause 80, wherein the pore size of        at least two of the two or more layers of the membrane material        are different.        83. A kit comprising:

a liposome extrusion device comprising:

-   -   a porous membrane; and    -   a component configured to position the membrane between a first        liquid container and a second liquid container, wherein, when        the component is attached to the first liquid container and the        second liquid container, an interior of the component is sealed        from the surrounding atmosphere; and a packaging configured to        hold the device.        84. The kit according to Clause 83, further comprising an        adapter configured to contain the liposome extrusion device.        85. The system according to Clause 84, wherein the adapter        comprises a cylinder with an outer surface concentric to an        interior surface of a centrifuge tube holder of a centrifuge.        86. The kit according to any of Clauses 83 to 85, further        comprising a set of standard fluorescently labelled beads.        87. The kit according to any of Clauses 83 to 86, further        comprising the first liquid container.        88. The kit according to any of Clauses 83 to 87, further        comprising the second liquid container.        89. The kit according to any of Clauses 83 to 88, wherein the        first liquid container comprises a centrifuge tube.        90. The kit according to any of Clauses 83 to 89, wherein the        second liquid container comprises a centrifuge tube.        91. The kit according to any of Clauses 83 to 90, wherein the        component comprises a first connector for connecting the        component to the first liquid container.        92. The kit according to Clause 91, wherein the first connector        comprises screw threads and an open end of the first liquid        container comprises corresponding screw threads.        93. The kit according to any of Clauses 83 to 92, wherein the        component comprises a second connector for connecting the        component to the second liquid container.        94. The kit according to Clause 93, wherein the second connector        comprises screw threads and an open end of the second liquid        container comprises corresponding screw threads.        95. The kit according to any of Clauses 83 to 94, wherein the        membrane is positioned between a first end of the component and        a second end of the component.        96. The kit according to any of Clauses 83 to 95, wherein the        component comprises a first subcomponent and a second        subcomponent removably attached to the first subcomponent.        97. The kit according to Clause 96, wherein the membrane is        positioned at an interface between the first subcomponent and        the second subcomponent.        98. The kit according to any of Clauses 83 to 97, wherein the        component has an inner diameter the same as an inner diameter of        the first liquid container or the second liquid container.        99. The kit according to any of Clauses 83 to 98, wherein the        membrane has a pore size of 1000 nm or less.        100. The kit according to any of Clauses 83 to 99, wherein the        membrane has a pore size of 500 nm or less.        101. The kit according to any of Clauses 83 to 100, wherein the        membrane has a pore size of 250 nm or less.        102. The kit according to any of Clauses 83 to 101, wherein the        membrane comprises one or more layers of a membrane material.        103. The kit according to Clause 102, wherein the membrane        material comprises a polymer.        104. The kit according to Clause 103, wherein the polymer        comprises polycarbonate.        105. The kit according to Clause 83 to 104, wherein the membrane        comprises two or more layers of a membrane material.        106. The kit according to Clause 105, wherein the pore size of        each of the two or more layers of the membrane material is the        same.        107. The kit according to Clause 105, wherein the pore size of        at least two of the two or more layers of the membrane material        are different.

Although the foregoing invention has been described in some detail byway of illustration and example for purposes of clarity ofunderstanding, it is readily apparent to those of ordinary skill in theart in light of the teachings of this disclosure that certain changesand modifications may be made thereto without departing from the spiritor scope of the appended claims.

Accordingly, the preceding merely illustrates the principles ofembodiments of the present disclosure. It will be appreciated that thoseskilled in the art will be able to devise various arrangements which,although not explicitly described or shown herein, embody the principlesof embodiments of the present disclosure and are included within itsspirit and scope. Furthermore, all examples and conditional languagerecited herein are principally intended to aid the reader inunderstanding the principles of embodiments of the present disclosurebeing without limitation to such specifically recited examples andconditions. Moreover, all statements herein reciting principles,aspects, and embodiments of embodiments of the present disclosure aswell as specific examples thereof, are intended to encompass bothstructural and functional equivalents thereof. Additionally, it isintended that such equivalents include both currently known equivalentsand equivalents developed in the future, i.e., any elements developedthat perform the same function, regardless of structure. The scope ofthe embodiments of the present disclosure, therefore, is not intended tobe limited to the exemplary embodiments shown and described herein.Rather, the scope and spirit of embodiments of the present disclosureare embodied by the appended claims.

1.-10. (canceled)
 11. A method for producing a uniform population ofliposomes, the method comprising: introducing a suspension of liposomesinto a liposome extrusion device comprising: a first liquid container; asecond liquid container in fluid communication with the first liquidcontainer; a porous membrane; and a component configured to position themembrane between the first liquid container and the second liquidcontainer; and applying a centrifugal force to the suspension ofliposomes in a manner sufficient to pass the liposomes through themembrane to produce a uniform population of liposomes.
 12. The methodaccording to claim 11, wherein the introducing comprises introducing thesuspension of liposomes into the first liquid container or the secondliquid container.
 13. The method according to claim 12, furthercomprising connecting the liquid container containing the suspension ofliposomes to the component.
 14. The method according to claim 13,further comprising connecting the other liquid container to thecomponent.
 15. The method according to claim 11, wherein the applyingthe centrifugal force is repeated one or more times.
 16. The methodaccording to claim 15, further comprising inverting the liposomeextrusion device between each repetition of the applying.
 17. The methodaccording to claim 11, wherein the applying the centrifugal forcecomprises spinning the liposome extrusion device in a centrifuge.18.-20. (canceled)
 21. The method according to claim 10, wherein theapplying comprises applying the centrifugal force such that thesuspension of liposomes is extruded from the first liquid container intothe second liquid container through the membrane, or wherein theapplying comprises applying the centrifugal force such that thesuspension of liposomes is extruded from the second liquid containerinto the first liquid container through the membrane.
 22. The methodaccording to claim 10, wherein the first liquid container comprises acentrifuge tube.
 23. The method according to claim 10, wherein thesecond liquid container comprises a centrifuge tube.
 24. The methodaccording to claim 10, wherein the membrane is positioned between afirst end of the component and a second end of the component.
 25. Themethod according to claim 10, wherein the membrane has a pore size of1000 nm or less.
 26. The method according to claim 25, wherein themembrane has a pore size of 500 nm or less.
 27. The method according toclaim 26, wherein the membrane has a pore size of 250 nm or less. 28.The method according to claim 10, wherein the membrane comprises one ormore layers of a membrane material.
 29. The method according to claim10, further comprising preparing the suspension of liposomes.
 30. Themethod according to claim 29, wherein the suspension of liposomescomprises a population of liposomes having heterogeneous sizes.
 31. Themethod according to claim 10, wherein the liposomes comprise afluorescent label.
 32. The method according to claim 10, wherein theuniform population of liposomes has an average diameter of 1000 nm orless.
 33. The method according to claim 32, wherein the uniformpopulation of liposomes has an average diameter of 500 nm or less. 34.The method according to claim 33, wherein the uniform population ofliposomes has an average diameter of 250 nm or less.